Unfortunately, the experiment quoted is not good enough to measure the
small electrical conductance of water. The conductivity of water alone
is not enough to let the light bulb light up, but we already know that
water does conduct enough (however little) to allow electrocution.
The table for the experiment cited has a column titled "Observations."
For water, the observation is "The light bulb would not light" and for
sugar water, the observation is "The sugar water is a non-conductor."
This second observation is really a conclusion drawn from a presumed
observation, that is, the bulb did not light up with sugar water (just
as it did not light up with water). The experiment cannot distinguish
between the conductivity of water and a sugar solution. It regards
them both as non-conductors.
Water conducts because it dissociates to a very small extent to
charged particles (ions). Tap water conducts more than pure water
since it also contains small amounts of dissolved ions.
shows the conductivity of very pure water (deionized water), tap
water, and sea water.
Table sugar is not made of ions and does not add to the conductivity
of water. At the same time, it will not make dissolved sodium ions
and chloride (or other) ions disappear; these would still be around to
conduct electricity even if sugar were added. I have not had much luck
in getting a table of the conductance of sucrose (sugar) solutions, so
I can't give exact numbers for the conductance of water versus
conductance of sucrose solutions. (There could be small changes in
conductance due to changes in dissociation of water, but I would not
expect this to affect the conductivity of tap water appreciably.)